#include <iostream>
#include <vector>
using namespace std;

class Solution {
 public:
  vector<int> sortArrayByParity(vector<int>& A) {
    int l = 0, r = A.size() - 1;
    while (l < r) {
      if (A[l] % 2 == 0)
        l++;
      else
        swap(A[l], A[r]), r--;
    }
    return A;
  }
};
